1. Field of the Invention
The present invention relates to an electrophoretic display device, and more particularly, to an electrophoretic display device and a method of fabricating the same.
2. Discussion of the Related Art
Until recently, display devices have typically included liquid crystal display (LCD) devices, plasma display panels (PDPs) and organic electro-luminescence displays (OLEDs). However, to meet consumer's requirements, various display devices are introduced.
Particularly, properties of a light weight, a thin profile, a high efficiency and a full color moving image displaying are required in the display device. To meet the properties, an electrophoretic display device is suggested. The electrophoretic display device uses a phenomenon that charged particles move to an anode or a cathode. The electrophoretic display device has advantages in a contrast ratio, a response time, a full color display, a cost, mobility and so on. Different from the LCD device, the electrophoretic display device does not require a polarizer, a backlight unit, a liquid crystal layer and so on. Accordingly, the electrophoretic display device has an advantage in production costs.
FIG. 1 is a cross-sectional view illustrating a method of driving an electrophoretic display device according to the related art. In FIG. 1, the related art electrophoretic display device 1 includes a first substrate 11, a second substrate 36 and an ink layer 57 interposed therebetween. The ink layer 57 includes capsules 63, and each capsule 63 has a plurality of white-dyed particles 59 and a plurality of black-dyed particles 61 therein. The white-dyed and black-dyed particles 59 and 61 are negatively and positively charged by a condensation polymerization reaction, respectively.
A plurality of pixel electrodes 28, which are connected to a thin film transistor (not shown), are disposed under the first substrate 11 and in each pixel region (not shown). Each of the pixel electrodes 28 has a positive voltage or a negative voltage. When the capsules formed to have various sizes, a filtering process is performed to obtain capsules having a uniform size.
When a positive or negative voltage is applied to the ink layer 54, the white-dyed particles 59 and the black-dyed particles 61 in the capsules 63 move according to polarities of the applied voltage. When the black-dyed particles 61 move upward, a black color is displayed. When the white-dyed particles 59 move upward, a white color is displayed.
FIG. 2 is a schematic cross-sectional view of the related art electrophoretic display device. In FIG. 2, the related art electrophoretic display device 1 includes a first substrate 11, a second substrate 36 and an ink layer 57 interposed therebetween. The ink layer 57 is disposed between fifth and sixth adhesive layers 51 and 53. Each of the first and second adhesive layers 51 and 53 is formed of a transparent material. A common electrode 55 is disposed under the second adhesive layers 53 to face the ink layer 57. The ink layer 57 includes capsules 63, and each capsule 63 has a plurality of white-dyed particles 59 and a plurality black-dyed particles 61 therein. The white-dyed and black-dyed particles 59 and 61 are negatively and positively charged, respectively.
The second substrate 36 may be formed of a transparent plastic or a glass, and the first substrate 11 may be formed of an opaque stainless steel. The first substrate 11 may be also formed of a transparent plastic or a glass. A color filter layer 40 of red (R), green (G) and blue (B) colors sub-color filters is formed under an entire surface of the second substrate 36. On the first substrate 11, a gate line (not shown) and a data line (not shown) are formed. The gate and data lines cross each other to define a pixel region P. A thin film transistor (TFT) Tr is formed at a crossing portion of the gate and data lines. The TFT Tr is disposed in each pixel region P. The TFT Tr includes a gate electrode 14, a gate insulating layer 16, a semiconductor layer 18 including an active layer 18a and an ohmic contact layer 18b, a source electrode 20 and a drain electrode 22. The gate and source electrodes are connected to the gate and data lines, respectively, and the gate insulating layer 16 covers the gate electrodes 14. The semiconductor layer 18 is disposed on the gate insulating layer 16 and overlaps the gate electrode 14. The source and drain electrodes 20 and 22 are disposed on the semiconductor layer 18 and spaced apart from each other.
A passivation layer 26 including a drain contact hole 27 is formed over the TFT Tr. The drain contact hole 27 exposes a portion of the drain electrode 22. A pixel electrode 28 is disposed on the passivation layer 26 and in each pixel region P. The pixel electrode 28 is connected to the drain electrode 22 through the drain contact hole 27. The pixel electrode 28 may be formed of a transparent conductive material, for example, indium-tin-oxide (ITO) or indium-zinc-oxide (IZO).
The electrophoretic display device 1 having the above elements uses ambient light, for example, natural light or room electric light, as a light source. The electrophoretic display device 1 can display images by inducing a position change of the white-dyed particles 59 and the black-dyed particles 61 in the capsule 63 depending on a polarity of a voltage applied to the pixel electrode 28.
FIGS. 3A to 3E are cross-sectional views showing a fabricating process for the related art electrophoretic display device. A region where a plurality of pixel regions are defined is referred to as a display region, and a region at a periphery of the display region is referred to as a non-display region.
In FIG. 3A, first and second adhesive layers 7 and 9 are formed on a front surface and a rear surface of a first carrier substrate 5, for example, a glass substrate, respectively. First and second metal thin film substrates 11 and 13 are attached to an outer surface of the first adhesive layer 7 and an outer surface of the second adhesive layer 9, respectively.
Next, an insulating layer (not shown) is formed on an entire surface of the first metal thin film substrate 11. A gate line (not shown) and a data line (not shown) crossing each other to define a pixel region P are formed on the insulating layer. A TFT Tr connected to the gate and data lines is formed in the pixel region P. Although not shown, in the non-display region, a gate pad electrode, which is connected to the gate line, and a data pad electrode, which is connected to the data line, are formed.
A passivation layer 26 is formed over the TFT Tr by coating an organic insulating material. The passviatin layer 26 is patterned to form a drain contact hole 27 exposing a drain electrode (not shown) of the TFT Tr in each pixel region P, a gate pad contact hole (not shown) exposing the gate pad electrode, and a data pad contact hole (not shown) exposing the data pad electrode.
A transparent conductive material layer (not shown) is formed on the passivation layer 26 by depositing a transparent conductive material. The transparent conductive material layer is patterned to form a pixel electrode 28 contacting the drain electrode of the TFT Tr through the drain contact hole, a gate auxiliary pad electrode (not shown) contacting the gate pad electrode through the gate pad contact hole, and a data auxiliary pad electrode (not shown) contacting the data pad electrode through the data pad contact hole. The first metal thin film substrate 11, where array elements, for example, the TFT Tr, the pixel electrode 28, and so on, are formed and the first adhesive layer 7, the first carrier substrate 5, the second adhesive layer 9 and the second metal thin film substrate 13 are stacked, may be referred to as an array substrate 22 for the electrophoretic display device.
Next, in FIG. 3B, third and fourth adhesive layers 32 and 34 are formed on a front surface and a rear surface of a second carrier substrate 30, for example, a glass substrate, respectively. First and second transparent substrates 36 and 38 are attached to an outer surface of the third adhesive layer 32 and an outer surface of the fourth adhesive layer 34, respectively. Each of the first and second transparent substrates 36 and 38 may be flexible.
A color filter layer 40 including sequentially arranged red (R), green (G) and blue (B) colors sub-color filters 40a, 40b and 40c is formed on the first transparent substrate 36. Each of the red (R), green (G) and blue (B) colors sub-color filters 40a, 40b and 40c corresponds to the pixel region P in the array substrate 22. The first transparent substrate 36, where the color filter layer 40 is formed and the third adhesive layer 32, the second carrier substrate 30, the fourth adhesive layer 34 and the second transparent substrate 38 are stacked, may be referred to as a color filter substrate 42 for the electrophoretic display device. On the color filter substrate 42, a black matrix (not shown) corresponding to a border region of the sub-color filters 40a, 40b and 40c may be further formed. The black matrix surrounds each pixel region P.
In FIG. 3C, an electrophoresis film 65 is attached onto the array substrate 22. The electrophoresis film 65 includes fifth and sixth adhesive layers 51 and 53, a common electrode 55 and an ink layer 57. The ink layer 57 is disposed between the fifth and sixth adhesive layers 51 and 53, and the common electrode 55 is disposed on the sixth adhesive layer 53 to face the ink layer 57. The ink layer 57 includes a plurality of capsules 63, and each capsule 63 has a plurality of white-dyed particles 59 and a plurality black-dyed particles 61 therein. The white-dyed and black-dyed particles 59 and 61 are negatively and positively charged by a condensation polymerization reaction, respectively. The fifth adhesive layer 51 is disposed to face the pixel electrode 28 such that the ink layer 57 is positioned between the common electrode 55 and the pixel electrode 28.
In FIG. 3D, the color filter substrate 42 is attached to the array substrate 22 to form a panel. The color filter substrate 42 is disposed to face the electrophoresis film 65.
In FIG. 3E, the first carrier substrate 5 with the first and second adhesive layers 7 and 9 and the second metal thin film substrate 13 is detached from the first metal thin film substrate 11. Also, the second carrier substrate 30 with the third and fourth adhesive layers 32 and 34 and the second transparent substrate 38 is detached from the first transparent substrate 36. As a result, the electrophoretic display device 1 can be obtained.
However, there are disadvantages in the above fabricating process for the related art electrophoretic display device. The fabricating process is very complicated. Namely, the array substrate requires processes of attaching the first and second adhesive layers on the front and rear surfaces of the first carrier substrate, attaching the first and second metal thin film substrates on the first and second adhesive layers, and forming the array elements, for example, the TFT or the pixel electrode, on the first metal thin film substrate attached on the first adhesive layer. Moreover, the array substrate requires processes of attaching the third and fourth adhesive layers on the second carrier substrate, attaching the first and second transparent substrates on the third and fourth adhesive layers, and forming the color filter layer on the first transparent substrate. In addition, unessential elements, for example, the first and second carrier substrates, are detached from the panel.
Furthermore, when unessential elements, for example, the first and second carrier substrates, which are required in a fabricating process for the electrophoretic display device but are not required in end products of the electrophoretic display device, are detached, there is an outer stress. As a result, there is a mis-align problem between the array substrate and the color filter substrate such that a display image quality is degraded.
Furthermore, there is a scratch damage on the first transparent substrate, which is formed of a relatively low hardness material, such as plastic, during attaching and detaching processes. The scratch also causes a display image quality being degraded.